PACK. 





Iriaiigularu nasi ( traiuvertaKi naai, cum- 

 yin.vMi; n, ins, Albin.) (n, Jig. 134), is a very 

 thin triangular muscle, placed transversely on 

 the middle of the side of the nose. To expose 

 its origin, the levutors of the upper lip must 

 be turned aside, and the skin of the nose very 

 carefully dissected off. Its origin is then seen 

 as a narrow slip from the inner part of the 

 canine fossa, below the ala nasi ; from this 

 point the fibres radiate inwards and upwards, 

 and expand into a very thin aponeurosis, 

 which crosses the ala nasi and the lateral car- 

 tilage of the nose to be confounded along the 

 median line with that of the opposite muscle, 

 and with the pyramidalis. Bourgery describes 

 two other origins, one superficial, attached to 

 the skin below and to the outside of the ala 

 nasi, and a middle one crossing and connected 

 with the fibres of the levator of the upper lip. 



Relations. It is covered at its origin by the 

 levator labii superioris alacqiie nasi, and inter- 

 nally by the integuments to which it super- 

 ficially adheres; it rests on part of the upper 

 jaw, on the cartilages of the ala, and on the 

 lateral cartilage. 



Its action is yet undetermined by anato- 

 mists, some considering it a compressor or 

 constrictor of the nose, others as a dilator or 

 elevator. Cruveilhier thinks that its action 

 varies with the form of the ala, which, when 

 convex, makes it a compressor, when concave 

 a dilator. Perhaps, as M. Bourgery suggests, 

 its action depends upon which extremity is 

 fixed, and that, when its base is fixed, its 

 superficial fibres dilate the nostrils and draw 

 the lip upwards and inwards, and that, when 

 the muscle acts towards its maxillary attach- 

 ment, it compresses the nostril. 



Depressor ala nasi (musrulus myrtiformii), 

 (Jig. 134.) To expose this muscle the upper 

 lip should be reversed, and the mucous mem- 

 brane divided on each side of the fraenum labii. 

 It is a short flat muscle, radiating upwards 

 from the myrtiform fossa of the upper jaw, 

 where it arises towards the ala of the nose, 

 into the posterior part of which it is inserted 

 below and internal to the dilator nasi. This 

 muscle really consists of two sets of fibres, 

 one which has been just described, the other 

 which is in front of this and is attached above 

 to the ala and septum of the nose, below to 

 the inner surface of the orbicular fibres. The 

 first set, or the naso-maxillary fibres, are de- 

 pressors of the ate and contractors of the 

 nostrils ; the second, or naso-labial fibres, are 

 elevators of the upper lip. 



Relations. It is covered by the mucous 

 membrane of the upper lip, by the orbicularis 

 oris, and by the levator labii superioris alaeque 

 nasi ; it covers the myrtiform fossa of the 

 upper jaw : its inner border is separated from 

 its fellow by the fraenum. 



A dilator alre nasi is described by Bourgery 

 as a little triangular muscle, consisting of 

 fibres placed underneath the skin lying on the 

 outside of the ala nasi, from the posterior part 

 of whose cartilages the fibres arise by a narrow 

 point, and then radiate upwards, outwards, 



Fig. 135. 



and downwards, to be mingled with the fibres 

 of the elevators of the lip, the orbicularis, and 

 the naso-labial, all being attached to the skin. 

 This muscle, according to Bourgery, directly 

 draws the ala outwards, and is consequently a 

 dilator of the nostril. 



The labial region presents in the centre, 1 . 

 a sphincter (the orbicularis oris), with which 

 are associated two muscles on each side, the 

 depressor labii superioris and the levator labii 

 inj'eriorii: all these are contractors or com- 

 pressors of the lips: 2. a number of anta- 

 gonist muscles or dilators, which comprise 

 many muscles, which on each side radiate 

 from the lips, or from their commissure at 

 different angles. They are, above, the levator 

 labii superioris proprius and the zygomaticus 

 minor; below, the depressor labii inferioris at 

 the commissure, the buccinator, the levator 

 anguli oris, and the depressor anguli oris. By 

 some anatomists the muscles of this region of 

 the face are divided into, 1. the sphincter, 

 and, 2. the elevators and depressors of the 

 lips. 



Orbicularis or sphincter oris (7<i6ia/, Chains, 

 and Duin.) (o o, Jig. 134) is a thick oval 

 muscle, placed transversely around the aper- 

 ture of the mouth, which varies in size in dif- 

 ferent persons, but bears no relation to the size 

 of the buccal cavity. It extends above from 

 the free border of the upper lip to the nostrils, 

 and inferiorly from the free border of the lower 

 lip to the depression above the chin. Its 

 fibres, arranged in successive layers, consist 

 of two semi-elliptical halves, one superior, the 

 other inferior, which are on each side united 

 externally to the commissure of the lips by 

 decussating each other, and mingle also at 

 their circumference with the dilators which are 

 attached to it. These fibres are concentric, 

 with their curve towards the lips; the most 

 central run nearly in a horizontal direction 

 along the borders of the lips, and take a di- 

 rection forwards, which gives the prominence 

 to the lips which is so remarkable in the 

 Negro. The outer fibres are more curved, 

 and receive between their layers the extensors 

 of the lips, which are attached around them. 

 This is the only muscle of the face which has 

 no attachment to bone. 



Relations. The anterior surface is closely 



